Configuration and Management
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port forwarding allowing communication between certain Internet
applications and the local network. When UPnP IGD is enabled, programs
like MSN Messenger
®
and most network enabled games are allowed to
pass the NAT service.
To disable UPnP IGD, clear the Enable UPnP IGD check box on the NAT
page and click Apply .
2.7.2 Application Level Gateways
From a security perspective, certain Internet applications, for example FTP
applications that open additional ports upon transfer, are especially
problematic to handle. An Application Level Gateway (ALG) provides a
translation and transportation service for such a specific application.
Incoming data packets are checked against existing NAT and packet
filtering rules, IP addresses are evaluated and a detailed packet analysis is
performed. If necessary, the contents of a packet are modified and if a
secondary port is required, the ALG will open one. The Ericsson W20
includes ALG support for the following applications:
Table 3 ALG Supported Applications
Application Protocol Port
number
File Transfer Protocol (FTP) TCP 21
Trivial File Transfer Protocol (TFTP) UDP 69
The ALG for each application does not require additional configuration. The
supported ALGs can be enabled and disabled individually. To disable an
ALG, clear the corresponding check box on the NAT page and click
Apply .
2.7.3 Port Forwarding
Port forwarding is used to allow incoming access to a specific local network
device, for example an internal web server.
Note: Port forwarding requires a public IP address of the Ericsson W20.
The Ericsson W20 IP address is displayed on the Internet page. A
private IP address usually begins with 10, 172, or 192. In this
case, no incoming access from the Internet is allowed. For more
information on public and private IP addresses, contact your
service provider.
